﻿<p>This entity is a description of a panel within a door or window (as fillers for opening) which allows for air flow. It is given by its properties (<em>IfcPermeableCoveringProperties</em>). A permeable covering is a casement, such as a component, fixed or opening, consisting
essentially of a frame and the infilling. The infilling is normally a grill, a louver or a screen. The way of operation is defined in the operation type.</p>

<p>The <em>IfcPermeableCoveringProperties</em> are included in the list of properties (<em>HasPropertySets</em>) of the <em>IfcWindowStyle</em> or the <em>IfcDoorStyle</em>. More information about the permeable covering can be included in the same list of the window or door style using the <em>IfcPropertySet</em> for dynamic extensions. This particularly applies for additional properties for the various operation types</p>

<p>The <em>IfcPermeableCoveringProperties</em> does not hold a geometric representation. However it defines parameters which can be used to create the shape of the <em>IfcWindowStyle</em> (which is inserted by the <em>IfcWindow</em> into the spatial context of the project), or of the <em>IfcDoorStyle</em> (which is inserted by the <em>IfcDoor</em>).</p>
<p>The parameters at the <em>IfcPermeableCoveringProperties</em> define a standard permeable covering. The outer boundary of the panel is determined by the occurrence parameter assigned to the
<em>IfcWindow</em> or <em>IfcDoor</em>. It has to take the lining parameter into account as well. The position of the permeable covering within the overall window or door is determined by the
<em>PanelPosition</em> attribute.</p>

<p>Figure 2 illustrates the panel applied to the position within the lining, as defined by the panel position attribute. The following parameters apply to that panel: <em>FrameDepth</em>, <em>FrameThickness</em>.</p>

<table>
<tr><td><img src="../../../figures/ifcpermeablecoveringproperties.gif" alt="covering" width="400" height="215" border="0"></td></tr>
<tr><td><p class="figure">Figure 2 &mdash; Permeable covering properties</p></td></tr>
</table>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC2.0, it had been renamed from
<em>IfcPermeableCovering</em> in IFC2x.
</blockquote>
<blockquote class="change-ifc2x4">
IFC4 CHANGE&nbsp; Supertype changed to new <em>IfcPreDefinedPropertySet</em>.
</blockquote>
